Carburetor



Jam-'1, 1935. A. M. PRENTlss' j 17,986,408

.GARBURETOI Filed Feb. 19, 1951 ATTORNEY Patented Jan. l, 1935 I iUNITED STATES PATENT oFFIcE 1,986,408 CARBURETORl Augustin M. Prentiss,San Antonio, Tex., assignor to Bendix Stromberg Carburetor Company,South Bend, Ind., a corporation otlllinois Application February 19,1931, Serial No. 518,898 10 Claims. (Cl. 261-34) This invention,pertains to carburetors` for Still another object of my invention is topromobile internal combustion engines and more vide a temperaturecontrol of an acceleration particularly has reference to temperaturecontrol pump which is fully automatic in action and of accelerationpumps therefor. requires no operating adjustments.

1 5 It has long been known in the carburetor art A still further objectis to provide a simple 6 that the amount of additional fuel required forSelf-contained device for this purpose which does accelerating theengine when the throttle is sudnot discharge liquid fuel or vaporoutside the denly opened varies with the temperature of the carburetorWhere it may constitute a fire hazard. engine and carburetor. Thus, fora cold engine With these and other objects in view which l a relativelylarge accelerating charge of liquid may be incident to my improvements,my invenl0 fuel is required, and as the engine warms up a tion consistsin the combination and arrangegradually decreasing amount ofaccelerating fuel ment of elements hereinafter 'described and ilisneeded until a certain temperature is reached lustrated in theaccompanying drawing, of when no accelerating fuel is necessary, and ifwhich:

l5 any is supplied, it not only does not assist accel- Figure 1 shows incentral longitudinal section 15 eration, but actually hinders it. acarburetor embodying my improved accelera- The problem has heretoforebeen to control tion pump. the output of the acceleration pump or devicein Figure 2 is a central longitudinal section of accordance with theserequirements, and several the Cylinde'l 0r body 0f my improved Dump- Y2o schemes have been proposed for this purpose. Figure 3 is a bottomplan view of the same. 20

These generally have depended upon either reg- Referring specifically toFigure l, the referulating the air pressure on the liquid fuel chamencenumeral 1 denotes the body of the carber which supplies the acceleratingcharge, by buretor which consists of the usual air intake means of athermostatically controlled valve, or 2, mixing chamber 3, and mixtureoutlet 4, convarying the stroke of the acceleration pump by trlled by athIOttle Valve 5- Cast integrally 25 l some thermally responsiveelement. Both of with the body 1 is a liquid fuel float chamber 6,

, these schemes are attended with certain disadwhich iS Supplied Withliquid fuel by a pipe 7. vantages. The thermostatic air valves do notleading to a, main SupplyL tank (not Shown). give a suillciently closecontrol of the volume of Within the chamber `6 is a float 8 which actson accelerating charge as related to the tempera.- valve 9 to maintainthe level of the liquid fuel 30 ture, because the length and duration ofthe in said chamber at the normal static level indistroke oi' the pistoncreating the air pressure incated by the line Z-Z. tluences the amountof the accelerating charge Positioned within mixing chamber 3 is a mainfar more than the thermostatic valve can comfuel nozzle 10 whichcommunicates through a pensate. Also they depend upon thetemperapassageway 11 and port 12 with float chamber 35 ture of the airwhich is-often different from that 6. Port 12 is controlled by a needlevalve 13 of the liquid fuel. And the method of varying which servestoregulate the main jet discharge the stroke of the pump does not give asuillcientand thus controls the normal operating mixture. ly responsivedevice when suction controlled and The `slow speed or idley feed isdelivered 40 materially increases the difiiculty of operating through apassageway 14 which runs from noz- 40 the throttle when the pump ismechanically conzle 10 to a plurality of ports 15 and 16 which nectedthereto. bestride the throttle 5 when in closed position,

An object of this invention is to overcome the in a well known manner.above difculties by providing a form of thermo- Integral with the body 1is an extension 17 static control of the output of the acceleratinghaving a Cylindrical bOl've 13 in WhiCh leClDIO- 45 pump which does notnecessitate or depend upon cates a piston 19 as clearly shown inFigure 1. air pressure for varying the stroke of the pump, The cylinder18 communicates with the mixbut which shunts a portion of theaccelerating ture outlet`4 and (when the throttle is open) charge backto the liquid fuel (float) chamber mixing chamber 3, by means of apassageway depending upon the temperature. p 20 and port 21. so thatfluctuations in vacuum 50 Another object of my invention is to providein the mixture outlet and mixing chamber are a temperature control foran acceleration pump transmitted to the cylinder 18 and actuate thewhich depends primarily upon the temperature piston 19 in opposition toa spring 22 which is of the liquid fuel and not upon the temperaturepositioned within the piston 19 as shown in of the air or body of thecarburetor. Figure 1. 56

' chamber 6 and is fuel at all times. At a short distance below its-upper end, sleeve 26 is provided with an annular groove 27 for thereception of an expansion ring 28 (see Figures 1 andv 2). At a pointjust below the threads 25, sleeve 26 is split into a plurality ofsegments 29, of which four are shown in Figures 2 andi 3, and the sleeveis so designed that at a certain predetermined temperature, segments 29abut each (other closely so that there is substantially no liquidleakage therebetween. For this purpose sleeve 26 is made of an elasticmetal having a relatively low coefficient of expansion, such, (forexample) as invar. steel, and the segments 29 are given such an initialstress as will make them tend to cling tightly at -all times.

The ring 28 is made in two semi-circular parts of a metal of relativelyhigh coefilcient of expansion, such V(for example) as aluminum, so thatwhen this ring is assembled in groove 2'7, its inner surface is flushwith the bore of sleeve 26 while its outer surface abuts and bearsagainst the inner surface of groove 2'7 as clearly shown in Figure 2.Withthis arrangement, it is clear that as the temperature of the liquidfuel in oat chamber 6 raises thetemperature of the sleeve 26 and ring28, the ring having a relatively high coefficient of expansion ascompared to the sleeve, will undergo a correspondingly greaterenlargement than the sleeve, thus forcing apart the segments 29 asshownV in dotted lines in Figures 2 and 3.

. Moreover, the difference in coefcients of expansion between the sleeve26 and ring 28 can be made to give a predetermined amount of spread, oropening, between the segments 29 for each degree rise in temperature. Inother words, the amount of opening between the segments 29 is calibratedwith the temperature. When the temperature of the liquid fuel in chamber6 falls, the sleeve 26 and ring 28 cool to the same degree, and Vas thering 28 contracts faster and more than sleeve 26, the segments 29 are-free to assume their normal abutting position which the initial stressin the metal of the sleeve 26 compels them to take, when the ring 28 hascontracted enough to permit it.

It will be noted that by locating the ring 28 near the top of sleeve 26,the effect on the sleeve of the ring expansion is multiplied .severalfold, depending upon the ratio of the distance from the top of thesegments 29 to the center line of the ring as compared to the totallength of the segments 29. Thus, if the distance from the top of thesegments to the center of the ring is one-tenth the length of thesegments, the expansion of the lower end of the segments will be tenfold that of the ring. When the segments 29 abut each-other, which -istheir position at the lowest operating temperature of the carburetor,the sleeve 26 defines a cylinder in which the head 24 of piston 19travels with a free running nt which is made as liquid-tight as possiblewithout binding.

'Positioned with sleeve 26 near its lower end is a piston 30 whichreciprocates within the sleeve 26 and normally closes the lower endthereof. Pimm so slides upon a stud 31 which is fixed to attached, as byscrew threads 25, to

the bottom of the float chamber 6 as with screw threads 32. Stud 31 hasan enlarged conical head 33 and a central longitudinal passageway 34that communicates with passageway 11. Head 33 forms a seat for thepiston 30 which is normally held in contact therewith by a spring 35 soas to close the end of passageway 34 and cut off communication betweenthe interior`of sleeve 26 and passageway 11.

' The clearance between the piston 30 and sleeve 26, when segments 29are abutting, is such that when head 24 descends slowly, as when thethrottle is slowly opened, the liquid fuel escapes between the walls ofthe sleeve 26 and the piston 30 back into the float chamber 6 withoutunseating piston 30 and opening passageway 34. Thus no acceleratingcharge is delivered to the mixing chamber 3 through nozzle 10. If,however, head 24 quickly descends, as when the throttle 5 is quicklyopened, the clearance between sleeve26 and piston 30 is too small topermit the escape of liquid fuel from sleeve 26 without unseatingpiston30 and discharging liquid fuel through passageways 34 and 11, and nozzlel into mixing chamber 3. If now the segments 29 spread with a rise intemperature it is clear that a portion of the liquid fuel charge insleeve 26 escapes back into float chamber 6 even when the throttle isquickly opened and the head 24 quickly descends, thus subtracting fromthe total accelerating charge delivered by the pump. Moreover, it isequally clear that as the segments further spread with a further rise intemperature, a further corresponding reduction is made in the amount 'ofthe accelerating charge delivered by any stroke of the pump.

'Thus the output of the pump isgradually reduced proportionately withrise in temperature from a maximum at the coldest operating temperatureof the carburetor to a minimum, or nothing, at the highest operatingtemperature of the carburetor, and perfect temperature compensation orcontrol results.

From lthe arrangement described above and shown in Figure 1, it isapparent that when head 24 quickly descends and segments are not toowide open, piston 30 will be unseated and forced down by the pressure onthe liquid fuel in sleeve 26, but as the liquid fuel escapes throughpassageway 34 and between piston 30 and sleeve 26, spring will andreturn it to its seat thus clearing the sleeve 26 of liquid fuelprovided head 24 has not risen in the meantime. This return stroke ofpiston 30 serves to prolong the discharge of liquid fuel.

from the accelerating pump.

In this connection, however. it will be noted that piston 30 extendssomewhat above the top of stud 31 so that if head 24 descends to itslowermost position it will mechanically contact with piston 30 and holdit slightly oil its seat thus keeping open thev passageway 34. Thisserves an important function, namely that of an economizer. Forl it willbe observed that the only conditions under which piston 19 would descendto the bottom of its stroke and remain there for any appreciable lengthof time is when gradually force piston 30 upward the throttle is wideopen and the engine is turn-l ing over slowly under a heavyload. Thenthe, vacuum in mixing chamber 3 and outlet 4 is so weak that spring 22keeps piston 19 at the bottom of its stroke until either. the enginegains speed or the opening of the throttle is restricted. In order thatliquid fuel may ow from oat chamber 6 to the mixing chamber 3 when head24 is holdingpiston 30 ofl' its seat, head 24 is provided with aplurality of radial grooves 36 which provide a channel from the spacebetween piston 30 and sleeve 26 and the end of passage- Way 34.

It will be notedthat when segments 29 are spread apart, liquid fuelenters the sleeve 26 above head 24 and surges in and out of sleeve 26 ashead 24 falls and rises. This serves tol steady the movements of piston19 and prevents chattering with small 'sudden fluctuations of vacuum inmixture outlet 4. It also insures that the sleeve 2 6 will always be atthe temperature of the liquid fuel.

While I have shown ferred embodiment of my invention, I desire it to beunderstood that I do not limit myself to the constructional` de ilsdisclosed by way of illustration, as it is apparent that these may bechanged and modified by those skilled in the art without departing fromthe spirit of my invention or exceeding the scope of the appendedclaims. I

I claim:

1. In a carburetor, an acceleration pump comprising a cylinder having arelatively low thermal coeilicient of expansion, an element havlng arelatively high thermal coefficient of expansion associated withsaidhcylinder so that, as the temp/rature rises, the cylinder isexpanded in increasing ratio from one end to the other by said element.

`2. In a carburetor, an acceleration pump comprising a cylinder composedof a material of relatively low thermal expansion, an annular member ofrelatively high thermal expansion positioned within said cylinder sothat, as the temperature rises, the cylinder is enlarged in increasingratio from one end to the other by said member.

3. In a carburetor, an acceleration pump comprising a cylinder dividedfor a portion of its length into a plurality of segments and meanswithin said cylinder for spreading said segments apart in lineartemperature.

4. In a carburetor having a chamber containing liquid fuel, anacceleration pump comprising a cylinder supplied with fuel from saidchamber and divided for a portion of its length into a plurality ofsegments, and means within said cylinder responsive to the temperatureof the liquid fuel for spreading apart said segments in directproportion to a rise in temperature of the liquid fuel, whereby aportion of said liquid fuel escapes back into said chamber.

5. In a carburetor having a liquid fuel chamber, an acceleration pumpcomprising a cylinder suppliedwith fuel from said chamber, a pluralityof pistons in` said cylinder adapted to proportion to an increase in anddescribed the pre-- lchamber as long as low apply pressure to the liquidfuel therein, one of said pistons controlling an outlet port-throughwhich the accelerating charge of liquid is delivered from said cylinder,said last mentioned piston holding said outlet port closed until thepressure on the liquid fuel in said cylinder reaches a predeterminedamount.

6. In a carburetor having a mixing chamber and a liquid fuel chamber, anacceleration pump comprising a cylinder supplied with liquid fuel fromsaid chamber, a plurality of pistons in said cylinder, one of saidpistons being responsive to the vacuum in said mixing chamber, the otherof said pistons controlling an outlet port from said cylinder to saidmixing chamber, said first `mentioned piston being adapted under lowvacuum in said mixing chamber to hold down said second mentioned pistonand maintain said port open so that additional fuel is continuously fedfrom said liquid fuel chamber to said mixing vacuum obtains in saidmixing chamber.

7. In a carburetor having a oat chamber, a reciprocating accelerationpump in said chamber comprising a cylinder, a piston in said cylinderand temperature-responsive means for admitting liquid fuel from saidchamber to said cylinder whereby the amount of accelerating chargedelivered by said pump is inversely proportional to the temperature ofthe liquid fuel under certain operating conditions.

8. In a carburetor having a oat chamber, a reciprocating accelerationpump in said chamber comprising a cylinde'r, a piston in said cylinderand temperature-responsive means for admitting liquid fuel from saidchamber to said cylinder, and for returning said liquid fuel to saidchamber, whereby the amount of accelerating charge delivered by saidpump is inversely proportional ture-responsive means for admittingliquid fuelfrom said chamber to said cylinder above and below saidpiston, whereby minor uctuations in the movements of said piston aredamped and the amount of accelerating charge delivered by said pump isinversely proportional to the temperature of the liquid fuel.

AUGUSTIN' M. PRENTISS.

